In a large bowl, or the bowl of a food processor fitted with a metal blade, whisk or pulse the sugar and lime zest until mixed. Add the eggs, lime juice, and vanilla and process or whisk for a few seconds to combine. Add the melted margarine and oil and process or whisk for 10 seconds. Add the flour, baking powder, and salt to the batter and process or whisk again. Add the poppy seeds and process or whisk to just mix in.

Use a silicone spatula to pour the batter into the prepared pan. Bake for 50 to 60 minutes, or until a wooden skewer comes out clean. (Do not discard the skewer, you will use it to glaze the cake.) Cook in the pan for 10 minutes. Remove from the pan and let cool on a rack.

Place the ingredients for the glaze in a small, heavy-bottomed saucepan and bring to a boil. Turn the heat down to medium and cook uncovered, stirring often, for 4 to 5 minutes, until the glaze thickens.

Place the cake on aluminum foil or on a metal rack over a cookie sheet. Take the skewer you used to test the cake and poke holes all over the top and sides of the cake. Use a brush to brush the glaze all around the cake, making sure to cover all the sides, including the sides facing the inside of the cake. Use up all of the glaze; it usually takes two times around to brush the entire cake.

Notes:

Yield: Serves 12 - 15Once the glaze has set and cake is completely cooled, store covered in plastic at room temperature for up to five days or freeze wrapped in plastic for up to three months.